Device for uniformly charging a non-planar electrophotographic plate

ABSTRACT

Apparatus for uniformly charging the curved surface of an insulating member. In a first embodiment, a single corona discharge electrode is mechanically coupled to a follower member which is maintained in contact with the non-charging surface of the insulating member. The distance between the follower member and the discharge electrode is maintained at a constant value as the member moves relative to the discharge electrode, the charge being deposited uniformly over the charging surface of the insulating member. In a second embodiment, the follower member and discharge electrode are arranged to uniformly deposit charge on a selected portion of the insulating member.

United States Patent [1 1 Takahashi et a1.

[451 July 3, 1973 DEVICE FOR UNIFORMLY CHARGING A [56] References Cited NON-PLANAR ELECTROPHOTOGRAPHIC UNITED STATES PATENTS PLATE 2,747,152 5/1956 Greene 219/125 X [75] Inventors: Isoji Takahashi; Ma amichi Sam; 3,183,352 5/1965 Brandt et a1 250/49.5 g t H j f A k Japan 3,303,401 2/1967 Naumann et al. 317/262 [73] Assignee: Xerox Corporation, Stamford, Conn. Primary Examiner wimam R Lindquist [22] Filed: Feb. 9, 1972 Attorney-James J. Ralabate [21] Appl. No.: 224,990

[57] ABSTRACT Related US. Application Data A t f f l h m d f f ppara us or um orm y c argmg e curve sur ace 0 [63] Commune of 1970' an insulating member. ln a first embodiment, a single corona discharge electrode is mechanically coupled to [30] Fore'gn Application Prlomy Data a follower member which is maintained in contact with Nov. 26, 1969 Japan 44/94931 the nomcharging surface of the insulating member The distance between the follower member and the dis- [52] CL 1 18/620 118/637 charge electrode is maintained at a constant value as 317/262 A the member moves relative to the discharge electrode, [51 Int. Cl G03g 15/02 the charge being deposited uniformly over the charging [58] Field of Search 117/17, 93.1;

118/620, 637; 204/312; 250/495 R, 49.5 TE, 49.5 GC, 49.5 ZC, 49.5 TC, 52, 201, 202; 219/121 EB, 121 R, 121 P, 121 L, 125 PL; 317/262 A; 318/570; 315/3, 17

surface of the insulating member. In a second embodiment, the follower member and discharge electrode are arranged to uniformly deposit charge on a selected portion of the insulating member.

4 Claims, 5 Drawing Figures Patented July 3, 1973 3,743,830

2 Sheets-Sheet l INVENTORS ISOJI TAKAHASHI MASAMICHI SATO BY 3 TORU HONJO ATTORNEY Patented July 3, 1973 2 Sheets-Sheet I DEVICE FOR UNIFORMLY CHARGING A NON-PLANAR ELECTROPHOTOGRAPI-IIC PLATE This is a continuation, of application Ser. No. 86,553, filed Nov. 3, 1970.

BACKGROUND OF THE PRESENT INVENTION Electrostatically charging a photoconductive insulating layer on a conductive support having an irregularly shaped or curved surface with any of the conventional corona charging devices results in uneven distribution of charge in which the raised area of the curved surface accepts a higher potential while the depressed area are charged to a lesser potential, since the spacing between the corona discharge electrode and the layer surface varies from location to location. When image exposure and subsequent development are carried out onto such an unevenly charged layer, an acceptable quality image is not produced. It is therefore necessary to produce uniform charging of the layer throughout the area on which the image is to be formed.

Conventionally, charging devices for use in electrophotography have been designed to charge flat or cylindrically shaped members and were not suitable for charging members having complex, rugged curved surfaces. Rapid advances in and expansion of applications of electrophotographic techniques have increased the demand to form images electrophotographically on such complex, curved surfaces on the entire area or predetermined limited area thereof. A new type of charging device is required for such electrophotographic members. 1

SUMMARY OF THE PRESENT INVENTION The present invention provides apparatus for charging the entire surface or predetermined portions of the surface of an insulating member, the surface of the member being irregularly shaped. In particular, a corona discharge electrode is maintained at a predetermined distance above the surface of the member and at a constant distance from a follower member, the follower member being maintained in contact with the non-charging surface of the member. When the discharge electrode is energized, a substantially uniform charge is produced on the surface of the insulating member.

It is an object of the present invention to provide apparatus for uniformly charging an irregularly shaped insulating member on its entire surface or portions thereof. I

It is a further object of the present invention to provide apparatus for uniformly charging the curved surface of an insulating member, the member being of a substantially uniform thickness.

DESCRIPTION OF THE DRAWING For a better understanding of the invention, as well as other objects and further features thereof, reference is made to the following description which is to be read in conjunction with the accompanying drawing wherein:

FIG. 1 is a schematic cross-sectional view of charging apparatus in accordance with the present invention;

FIG. 2 is a perspective view of one embodiment of the present invention;

FIG. 3 is another embodiment of the present invention;

FIG. 4 is a cross-sectional view of the embodiment I shown in FIG. 3 at the plane IV-IV in FIG. 3; and

FIG. 5 shows a cross-sectional view of still another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, one embodiment of charging apparatus of the present invention is shown. The apparatus uniformly charges a plate 13 comprising electrophotographic, or photoconductive layer 12 formed on curved conductive substrate 11 of a substantially uniform thickness. Typical electrophotographic materials include cadmium sulfide, selenium, zinc oxide, sulphur selenium, etc. According to the teachings of the present invention, a follower 14 is utilized which is of a structure that enables it to smoothly move along the rear, or non-charging, surface of substrate 11. At a predetermined distance from follower 14 and above the front surface of the plate 13 is provided a corona discharge electrode 15, with which the follower 14 is connected by suitable mechanical, magnetic or electromagnetic means as shown by a broken line 16 so as to keep a constant distance therebetween.

The curved plate or recording member 13 is inserted between corona discharge electrode 15 and follower 14. With the follower kept in contact with the rear surface of the substrate 11, the recording member 13 is moved in the direction of arrow 17 by a driving means (not shown). It should be noted that the recording member 13 may be maintained stationary and the follower 14 moved relative thereto. When a high potential is applied to corona discharge electrode 15, the electrophotographic layer 12 is substantially uniformly charged, since the distance between the discharge electrode l5 and the layer 12 beneath the electrode is always kept constant by virtue of the presence of follower 14. This distance is equal to that between the top of the follower and the tip of the discharge electrode minus the thickness of the plate member 13.

When the plate member 13 forms an indented surface relative to the electrode 15, it may occur that other portions of the plate member surface come closer to the electrode than the area on the line connecting the discharge electrode 15 and the follower 14. To avoid such occurrence the predetermined distance between discharge electrode 15 and follower 14 may be selected to be shorter than the minimum radius of ourvature in the plate member to be charged.

When plate member 13 is linear along a direction of relative movement between discharge electrode 15 and the plate member 13, but not linear along the direction perpendicular to it, the corona discharge electrode 15 may be made of one or more parallelly oriented wires as shown in FIG. 2 or a row of pin electrodes.

In order to charge a plate having irregularities in both directions, a single pin electrode or closely spaced multiple pin electrodes must be used. Similarly, the follower 14 may be a long cylinder as shown in FIG. 2, an array of short cylinders or an array of multiple balls extending in the direction along which the member is linear flat. When plate member 13 has a rugged or irregular surface in any direction, the follower 14 preferably comprises a single ball as will be described hereinafter with reference'to FIG. 3. Moreover, to ensure accurate following of the rear surface of plate member 13, the ball or cylinder preferably has a radius not larger than the minimum radius of curvature in the configuration of the member to be charged. In addition, the follower 14 should rotate smoothly and freely around its axis or center in order to accomplish a smooth movement along the rear surface of the plate member.

FIG. 2 illustrates one embodiment of the present invention suitable for charging an electrophotographic member, such as corrugated plate 21, which is linear in one direction. The apparatus comprises a charging unit and a cylindrical follower 24, the former comprising a wire electrode 23 mounted in a grounded shield 22. The shield 22 in the embodiment illustrated has a generally inverted U-shaped cross-section. The follower 24 has a radius smaller than the minimum radius of curvature of the electrophotographic member 21 and is setup rotatably and in the horizontal plane. The electrode 23 and the follower 24 are linked with a pair of connecting members 25 and the wire 23 is maintained parallel both to the cylinder 24 and to the surface of member 21 with a spacing suitable for corona charging. In addition, the spacing may be selected to be less than the minimum radius of curvature of the member 21. The members 25 have a structure capable of adjusting the distance between wire electrode 23 and follower 24, and are held by main supports 27 through springs 26 which keep the cylinder 24 in contact with the electrophotographic member 21, exerting a recovery force in the direction shown by the arrow 28 against a force downwardly applied to the follower 24 by member 21.

To charge the electrophotographic member, or plate 21, the member is inserted between the follower 24 and the wire electrode 23 with the electrophotographic layer up in such a manner that the follower 24 is in contact with the highest portion of he member with the springs being ultimately contracted or compressed. A support 29 is used to set the member 21 in a horizontal position. The member 21 is then driven in the direction shown by arrow 30 by a driving means (not shown) at a constant speed with a high electrical potential applied to the wire electrode 23, whereby the corona discharge generated at wire electrode 23 impinges the electrophotographic layer on member 21. As the member 21 moves and the follower 24 goes from a peak to a valley, member 21 suppresses the follower downwards against the recovery force of the springs 26. As the raised portion of member 21 comes to the follower 24, the suppressing force on follower 24 decreases and the springs 26 pull up the follower vertically.

In such a manner, during the charging operation the follower 24 shifts up or down together with the corona electrode 23 in accordance with the shape of the member 21, a constant distance being maintained between the surface of the member 21 and the electrode 23, thereby producing substantially uniform charging on the surface of member 21.

FIGS. 3 and 4 illustrate charging apparatus useful for charging an irregularly shaped plate 31 having a rugged structure along any direction. A spherical follower 33 which preferably has a radius smaller than the minimum radius of curvature of plate 31 is rotatably supported by and on the top of a vertical member 32. A stylus electrode 35 vertically held by a holder 34 is also provided. The follower 33 and the electrode 35 are mechanically united with a connector (not shown) in such a manner that a perpendicular line including the stylus electrode 35 passes the center of the sphere 33 with a predetermined distance therebetween suitable for charging the surface of plate 31, the distance being adjustable depending upon the shape of plate 31.

Plate 31 is placed on fixed supporting rods 37 via springs 36 and supports 38. As the springs are compressed by the gravitational force of the plate, the supports 38 are lowered until the rear surface of plate 31 contacts follower 33. The assembly is set in such a manner that the follower 33 is always in contact with the rear surface of plate 31.

As plate 31 is driven at a constant speed in the direction shown by the arrow 39 by a suitable driving means (not shown), the assembly comprising the follower 33 and the electrode 35, a high electrical potential being applied to electrode 35, scans the plate 31 in the direction perpendicular to that of the movement of the plate at a constant speed whereby corona ions generated at the electrode impinges upon the surface of the member 31. During the charging operation follower 33 rises or falls together with the corona electrode 35 in accordance with the shape of the plate 31. A constant distance is thus maintained between the surface of plate 31 and the electrode 35.

Instead of moving the assembly relative to the plate 31, the plate 31 may be moved in the direction perpendicular to arrow 39 reciprocally at the same time it is moving in the direction of arrow 39.

In order to insure that the charging of the entire surface of the plate member shown in FIGS. 2, 3 and 4 is accomplished, the charging operation may be controlled to start when the leading edge of he plate member first comes in contact with member 29 (support member 38 in FIGS. 3 and 4). Similarly, the charging terminates when the trailing edge of the plate member comes into contact with members 29 or 38. Accordingly, a control unit (not shown) can be utilized such that the corona charging circuit is closed when the leading edge passes the member 29 or 38 and opened when the trailing edge passes either member.

In order to insure that a uniform electrostatic charge is formed on the entire surface of the plate by the use of the apparatus shown in FIG. 2, the spacing between the follower 24 and members 29 may be selected to be equal to. half the width of the charge pattern which will be formed on the stationary plate under the electrode. In case of the apparatus shown in FIG. 3, the spacing is selected to be equal to the radius of the circular charge pattern which will be formed on the stationary plate by the pin electrode. The width or radius of such patterns can be altered depending on the distance between the corona electrode and the plate surface, and the potential applied to the electrode. v

The apparatus described above has a rather wide versatility for use in charging members having rugged, complex and irregular shaped surfaces. For industrial applications in which limited types of products are pro duced in a large quantity, however, another type of charging device is also useful since it is capable of se- -quentially charging a portion of a number of members which have a common, relatively simple configuration.

For example, FIG. 5 illustrates a device adapted to charge a portion of an electrophotographic layer provided on the outer surface of a plate having a crosssection of a circular arc. The charge formed on the surface of plate 41 is in the form of a doughnut. The plate 41 is placed on a pair of rollers 44 rotatably held by a pair of fixed shafts 43 which stretch out of a pair of side boards 42 maintained at ground potential. Each of the rollers 44 is always in contact with the inner or rear surface of the plate 41. A support 46 vertically rising upright from a motor 45 is fixed on the plate either mechanically, magnetically or electromagnetically. One of the rollers 44 (at the left hand of the figure) serves as the follower of the present invention. A pin electrode for corona discharge 47 is provided on the vertical line running through the center of the roller 44 with a spacing suitable for charging the outer surface of plate 41. The electrode 47 is fixed on an insulating support 48 made of, for example, acrylic resin. The support 48 connects each of the side boards 42.

As an high electrical potential is applied to the pin electrode 47, the driving motor 45 begins to rotate the plate 41. The inner surface of plate 41 remains in contact with both of the rollers 44. Thus the spacing between the end or tip of the electrode 47 and the surface of the plate 41 just under the electrode is kept constant. A charge pattern results having the form of a doughnut having a width equal to the diameter of the circular corona pattern which would occur without relative movement between the plate and the electrode.

By modifying the apparatus so that the roller 44 other than the one acting as the follower can shift vertically and is pushed upwards by means of spring, it can be also used to charge plates of various configurations having relatively mild rises and falls along the circular direction of the plate.

In the embodiments set forth hereinabove, an electrophotographic recording member comprising a conductive or semi-conductive substrate and a photoconductive insulating layer provided thereon has been subjected to charging with the use of the apparatus in accordance with the present invention. The charged member was assumed to be subsequently exposed to an image of light and shadow to form an electrostatic latent image. However, the apparatus of course, can also be used to charge and electrically insulating (not photoconductive) coating provided on a curved substrate. The charged coating may be, for example, utilized for ionography wherein the charged member is exposed to imagewise X-ray radiation whereby an ionized ambient atmosphere helps the surface charge to dissipate to form an electrostatic latent image.

While the invention has been described with reference to its preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the invention without departing from its essential teachings.

What is claimed is:

1. Apparatus for uniformly charging a surface of a non-planar member having a substantially uniform thickness as said non-planar member is moved in a predetermined direction, the apparatus comprising:

a corona discharge electrode disposed adjacent said surface at one side of said non-planar member,

a follower member maintained in contact with the opposite side of said non-planar member as said non-planar member moves along,

means for rigidly coupling said follower member to said corona discharge electrode to maintain them in alignment in a plane transverse to the direction of movement of said non-planar member and to maintain a constant spacing between said discharge electrode and said surface, and

a potential source for applying an electrical potential to said corona discharge electrode, whereby a substantially uniform charge is formed on said surface.

2. The apparatus as set forth in claim 1, wherein said non-planar member comprises a conductive substrate and a photoconductive insulating layer overlying said conductive substrate to define said surface, and said follower member underlies and is maintained in contact with said conductive substrate.

3. The apparatus as set forth in claim 1, wherein said non-planar member has a corrugation-like deformity occurring along the direction of movement of said nonplanar member, and said discharge electrode comprises a corona wire disposed transverse to the direction of movement of said non-planar member, said wire having a length at least equal to the width of said planar memher.

4. The apparatus as set forth in claim 3, wherein said non-planar member has a predetermined minimum radius of curvature, and said follower member comprises an elongated roller having a radius which is less than said minimum radius. 

1. Apparatus for uniformly charging a surface of a non-planar member having a substantially uniform thickness as said nonplanar member is moved in a predetermined direction, the apparatus comprising: a corona discharge electrode disposed adjacent said surface at one side of said non-planar member, a follower member maintained in contact with the opposite side of said non-planar member as said non-planar member moves along, means for rigidly coupling said follower member to said corona discharge electrode to maintain them in alignment in a plane transverse to the direction of movement of said non-planar member and to maintain a constant spacing between said discharge electrode and said surface, and a potential source for applying an electrical potential to said corona discharge electrode, whereby a substantially uniform charge is formed on said surface.
 2. The apparatus as set forth in claim 1, wherein said non-planar member comprises a conductive substrate and a photoconductive insulating layer overlying said conductive substrate to define said surface, and said follower member underlies and is maintained in contact with said conductive substrate.
 3. The apparatus as set forth in claim 1, wherein said non-planar member has a corrugation-like deformity occurring along the direction of movement of said non-planar member, and said discharge electrode comprises a corona wire disposed transverse to the direction of movement of said non-planar member, said wire having a length at least equal to the width of said planar member.
 4. The apparatus as set forth in claim 3, wherein said non-planar member has a predetermined minimum radius of curvature, and said follower member comprises an elongated roller having a radius which is less than said minimum radius. 